Does Google assert their patents positively, though? I'm not aware of the PageRank patent being much used, despite the fact that there's a whole cottage industry of "PageRank for X" search tools, who not only seem to infringe on the patent, but even advertise the fact that they use a PageRank-derived algorithm (see, e.g., eigenfactor.org).
I think your point is a good one but I am confident that, if Microsoft started using PageRank for Bing, a Google lawsuit (or at least a Stanford lawsuit for the benefit of Google) would be both swift and formidable.
PageRank-style algorithms are so fundamental to current search tech that I would be shocked if Microsoft wasn't using something along these lines on Bing.
